1. Field
Example embodiments relate to an infrared detector, and more particularly, to an infrared detector that is capable of detecting a wide bandwidth of the infrared spectrum.
2. Description of the Related Art
According to the principle of black body radiation, an object radiates a broadband electromagnetic wave that peaks in at a certain wavelength according to temperature. For example, an object radiates an infrared ray having a peak in a wavelength band of about 10 μm at room temperature. Bolometers are tools that absorb electromagnetic waves having an infrared (or terahertz) wavelength band radiated according to the principle of black body radiation, converts the absorbed electromagnetic waves into heat and then detects a temperature change due to the heat to measure radiation energy therearound.
Recently, in the development of micro electro mechanical system (MEMS) technologies, infrared detectors in which a plurality of microbolometers are arranged in a two-dimensional array are being designed. For example, thermal cameras, which are capable of acquiring thermo images, may use the infrared detectors. To realize a high-resolution thermal camera having high temperature accuracy, a pixel of a small size may be required. However, in a case where Salisbury screen type bolometers are used, in which a ground plate and a heat absorber are disposed at an interval of about λ/4 (where, λ is a centroid wavelength of an infrared wavelength band to be detected), when a screen having pixels decreases in size, an energy amount incident into the pixel may be reduced causing a decrease in temperature variations and a signal-to-noise ratio.
Lately, the use of bolometers using localized surface plasmon resonance (LSPR) is being proposed instead of using Salisbury screen type bolometers. Surface plasmon refers to a type of electromagnetic wave generated due to charge density oscillation of electrons that occur on a surface of a metal. Bolometers using a plasmonic absorber may overcome limitations of low absorption and low signal-to-noise ratio due to the LSPR.
However, since the plasmonic absorber may have relatively narrow bandwidth, it may be difficult to effectively absorb heat of the entire infrared region of about 8 μm to about 14 μm which is typically used for acquiring thermo images. Thus, it may be beneficial to increase the resonance bandwidth of plasmonic absorbers.